The present invention relates to a processing technique for image data in an electronic filing apparatus for use with an optical disk and the like. In particular, the present invention is directed to a divisional file method and a system for the image data used to realize high speed retrieving of a large-sized drawing and the like by referring to the image itself on an image display apparatus.
Recently, image file apparati have been practically utilized, and various retrieval systems thereof have been studied. As is known, a method for displaying an image for retrieval is very useful when image data is retrieved, since such a method can make a direct appeal to an operator, as compared with another retrieval method by way of a keyword and the like.
In general, a display screen of an image file apparatus has been standardized with the CCITT protocols. for instance, an original-sized display of an A4 size is fixed to 200 dots/inch (DPI). To the contrary, a size of an image to be handled is different such that a document size is from A0 to A3. More specifically, in the case where a data capacity (A0 to A3) of a document is larger than the screen capacity (standard in A4) of a display apparatus, an entire image cannot be displayed without further processing. Then, while an image is inputted, when an image having a display dot number greater than that of a screen of a display apparatus is inputted, a guide image is formed by uniformly reducing the entire image so as to fit this image to the screen of the display apparatus, and the guide image is read out and displayed during the retrieving operation to retrieve the desired image.
However, when a large-sized source image such as an A0 and A1-sized drawing is uniformly reduced so as to be fitted with a screen having the normal A4 size. In recording the image on a recording medium, such as an optical disk, the image is compressed due to the thinned-out operation affected during the reduction, and there is a problem that a distinguishing part of each image cannot be judged for legibility in reproduction.
Accordingly, one conventional method as described in JP-A-60-10771 has been proposed to solve the above-mentioned problem.
In accordance with this conventional method, when a source or original image is inputted into an optical disk device of a file apparatus, an operator selectively extracts an arbitrary partial image from the source image so as to form it as a guide image, and stores it together with the source image into the optical disk. Then, in a retrieval operation, the guide image within the optical disk is read out, and the guide images are successively and continuously displayed on a display screen so that a desired image is retrieved. When the desired image can be found from the displayed guide images, the source image corresponding to the guide image in concern is read out and then the retrieval operation is accomplished.
In accordance with the above-mentioned prior art, since the distinguishing part of the source image can be observed at a glance, whereby an operator can immediately specify the source image, a retrieval can be realized in which convenient-to-use images are successively displayed to realize retrieval based on the contents thereof.
In the above-mentioned prior art, since the guide images are separately formed with respect to the source images and stored together with the source images in the image storage device, such as an optical disk, an extra file capacity for storing such guide images is required. Generally, since the amount of data in an image is large, the extra file capacity becomes large. In particular, when a plurality of guide images are formed with respect to each source image, the required file capacity becomes large. As a result, the number of images which can be stored in an optical disk for providing the file capacity is reduced.
In the case where, for instance, a 1/8 partial image of a source image is extracted therefrom so as to form a single guide image, image data is increased by 12.5% of that of the source image.
Further, if a source image cannot be specified by a guide image, the source image must be specified by observing a partial image other than the guide image of the source image. However, according to the conventional method, the partial image except for the guide image must be observed by reading the source image so as to display this source image. However, at this time, if compressed data of a source image having a large size such as A0 and A1 sizes are read out from the optical disk and expanded into image data so as to be displayed on a screen, there occurs an inconvenience that the display speed is lowered. For example, a time required for reading from the optical disk, compressed data obtained by compressing image data on an image having an A0 size and for expanding the compressed data so as to produce the image data, is consumed 16 times longer than that required for an image having an A4 size. As a consequence, the time required for displaying an entire image having the A0 size on the screen becomes much longer than that for displaying an image having the A4 size, and therefore the machine interface is considerably deteriorated.
In U.S. Pat. No. 4,716,404 issued on Dec. 29, 1987, assigned to the present assignee, a method has been proposed in which a distinguishing part of the source image as a guide image is combined with memorandum information to perform the image retrieval operation. However, no reference is made to performing the file process of a source image having a large size.
Furthermore, the memorandum image forming technique has been disclosed in U.S. Pat. No. 4,808,987 issued on Feb. 28, 1989 assigned to the present assignee.